Near infrared photon-downshifting in Yb3+-doped titanates: The influence of intrinsic defects
Por:
Padilla-Rosales, Isela, Lopez-Juarez, Rigoberto, Lopez-Pacheco, German, Falcony, Ciro, Gonzalez, Federico
Publicada:
1 ene 2020
Resumen:
Powder samples of Yb3+-doped TiO2 (0.5 mol%) -exhibiting anatase and rutile phases- CaTiO3, SrTiO3 and Na0.5Bi0.5TiO3 were synthesized by the sol-gel and polymeric complex methods. The crystal structure, microstructure and optical properties of the powders annealed at 800 °C and 1000 °C for 1 h were investigated by X-ray diffraction, scanning electron microscopy, diffuse reflectance and photoluminescence spectroscopies, respectively. X-ray diffraction patterns show the presence of the expected crystalline phase for each compound. Reflectance spectra for all compounds exhibit a broad absorption band below 425 nm ascribed to the ligand-to-metal charge transfer (LMCT) O2- ? Ti4+ fundamental state. The Yb3+ excitation spectra for all titanates show a broadband being also compatible with the LMCT O2- ? Ti4+ state, indicating the energy transfer from the host to the Yb3+. Interestingly, the excitation band edges follow the same order as that of the optical bandgap energy of the investigated titanates. A conspicuous excitation band in the CaTiO3:Yb3+ provides evidence about the importance of intrinsic defects in the energy transfer process from the host to Yb3+. Photoluminescence emission and diffuse reflectance spectra in the visible and NIR, reveal an emission band that overlaps with the absorption band of the Yb3+, explaining reasonably well the energy transfer process from the host to Yb3+. According to each compound, the integrated intensity of the Yb3+ emission follows the order Na0.5Bi0.5TiO3 > CaTiO3 > SrTiO3 > TiO2. Finally, it is shown that titanates may downshift photons from UV to wavelengths where a crystalline-silicon photovoltaic solar cell has its higher spectral responsivity. © 2020 Elsevier B.V.
Filiaciones:
Padilla-Rosales, Isela:
Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, A.P. 55-534, Ciudad de México, Mexico
Univ Autonoma Metropolitana Iztapalapa, Dept Ingn Proc & Hidraul, AP 55-534, Ciudad De Mexico, Mexico
Lopez-Juarez, Rigoberto:
Unidad Morelia del Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro No. 8701, Col. Ex Hacienda de San José de la Huerta, Morelia, Michoacán C.P. 58190, Mexico
Univ Nacl Autonoma Mexico, Inst Invest Mat, Unidad Morelia, Antigua Carretera Patzcuaro 8701, Morelia 58190, Michoacan, Mexico
Lopez-Pacheco, German:
Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, A.P. 55-534, Ciudad de México, Mexico
Univ Autonoma Metropolitana Iztapalapa, Dept Ingn Proc & Hidraul, AP 55-534, Ciudad De Mexico, Mexico
Falcony, Ciro:
Departamento de Física, CINVESTAV IPN, A.P. 14-740, Ciudad de México, 7000, Mexico
CINVESTAV IPN, Dept Fis, AP 14-740, Ciudad De Mexico 7000, Mexico
Gonzalez, Federico:
Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, A.P. 55-534, Ciudad de México, Mexico
Univ Autonoma Metropolitana Iztapalapa, Dept Ingn Proc & Hidraul, AP 55-534, Ciudad De Mexico, Mexico
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